The present invention relates to a high temperature oil containment boom which allows for the in-situ burning of spilled or leaked oil during offshore oil spill cleanup operations. In-situ burning represents one of the most effective means of eliminating large quantities of spilled oil. If conducted properly, with due consideration for the temporary reduction of air quality and the potential for exposure to fire, the in-situ burning of an oil spill can result in the least detrimental overall impact to the environment.
The remoteness of many oil exploration, production, and transportation activities (e.g. Alaska), combined with the nature of the environment, provides ideal conditions for in-situ combustion. When considered in conjunction with mechanical cleanup, chemical dispersants, and natural elimination processes, burning often provides an important option when some of the other techniques alone are impractical. For this reason, the oil industry in Alaska and Canada has conducted numerous research efforts to identify the most efficient means of burning oil in place (Shell Oil Company et al., 1983; S. L. Ross Environmental Research Limited, 1983).
Such research has revealed that oil can be ignited and combustion sustained when the oil layer on water is at least 1 to 2 mm thick. As thicknesses increase beyond this minimum value, there is less tendency for heat loss to the underlying water, and therefore the chances are greater for efficient combustion. Thick oil layers have been consistently burned with efficiencies in excess of 95%, even under arctic conditions. To achieve such success through burning, it is important to concentrate any spilled oil as quickly as possible and to contain the burning oil so that winds and/or currents can help thicken the oil slick. During the burning process, temperatures in the order of 1100.degree. C. are common.
Conventional oil containment booms are elongated cylinders having a generally circular cross-section. These booms float in water with approximately one-third of the boom submerged below the surface of the water forming a floating barrier to the spilled oil. The booms are typically stored in a roll on the deck of a ship and deployed downwind of a spill where it floats on the surface of the water and temporarily contains the spill.
The TTI Geotechnical Resources Ltd. described a fireproof oilspill containment boom in a brochure and claimed the boom consists of alternate rigid flotation units 1.668 m long, 1.78 m high weighing 108.8 kg and flexible (accordion folded) panels 0.906 m long, 1.70 m high weighing 102 kg connected together by connectors 0.07 m long, 1.67 m high weighing 10 kg. The boom is of stainless steel construction and the maximum exposure temperature is stated to be 980.degree. C.
Another fireproof oilspill containment boom is described in literature from Globe International Inc. A Pyroboom fireproof oil spill barrier utilizes a unique blend of refractory and metallic materials in a woven fabric coated with a high temperature polymer coating (silicone rubber). Flotation is provided by a series of stainless steel hemispheres, containing a high temperature resistant, closed cellular material. Two such hemispheres with the woven fabric enclosed between them are bolted together to form spheres 16 3/16 inches (41 cm) in diameter and spaced 34 inches (86 cm) apart at their centerlines along the length of the woven fabric. The boom has an overall height of 30 inches (76 cm) with a draft of 20 inches (51 cm) and a freeboard of 10 inches (25 cm), and weighs 8 to 10 lbs. per lineal foot (11.9 to 14.5 kg/m). The operating temperature range of the boom is stated to be -55.degree. F. to +2400.degree. F. (-48.degree. C. to 1315.degree. C.).
A fire resistant oil containment boom system designated as the SeaCurtain ReelPak FireGard Oil-Fire Containment Boom System is described in a brochure issued by Kepner Plastics Fabricators, Inc. That boom system appears to comprise compartmented circular sections containing a continuous stainless steel coil wire covered with a double walled foam containing refractory fabric with an additional portion extending downwardly from the circular section, the bottom edge of the downwardly extending section having a chain ballast member attached thereto. The boom is stored on a reel from which it is deployed. The boom is stated to have operating temperature range from -40.degree. F. to over 2000.degree. F. (-40.degree. C. to 1093.degree. C.) and, depending on model, weighs 2.2 lbs to 4.2 lbs. per lineal foot (3.3 to 6.3 kg/m).
U.S. Pat. No. 4,537,528 is directed to a fireproof boom for containing a flammable pollutant on a water surface, the boom comprising a flotation member of foamed polypropylene and at least two layers of heat-resistant, water-sorbent material surrounding the flotation member and extending into the water in the form of a depending skirt. The skirt functions to draw water up into the layers of heat-resistant material forming steam in the presence of flaming pollutant thereby allowing only the outer layer of heat-resistant material to become slightly singed. It is understood that a bottom-tensioned, cylindrical-flotation fire containment boom is manufactured by Fire Control Inc. utilizing the teachings of said patent. The boom consists of multiple layers of fire-resistant, wicking fabric positioned over steel canisters for flotation. An additional sacrificial layer and a coarse, wire-mesh barrier are used externally for abrasion resistance.
U.S. Pat. No. 4,619,553 discloses an oil boom system which utilizes a multilayered, fire-resistant blanket, and is manufactured by Minnesota Mining and Manufacturing Company (3 M Company), the assignee of the present invention. The fire-resistant blanket is used as an add-on high temperature protective blanket to convert most conventional types of booms to a containment for burning oil. The blanket is placed about the periphery of the boom and is held in position by any number of fastening systems.
Still another oil boom system provided by Minnesota Mining and Manufacturing Company (3 M), the assignee of the present invention, is a high temperature oil containment boom which allows for the in-situ burning of spilled or leaked oil. The boom comprises an outer layer of polymer coated fabric, a first underlayer of high temperature resistant refractory fabric and a second underlayer of a high or intermediate temperature resistant refractory fabric which constrains and assists in retaining the integrity of a low density, high temperature resistant core. The layers are unified by sewing with high temperature resistant, ceramic thread or by mechanical fasteners.
Problems associated with the above mentioned fire containment oil booms are that they are either difficult to recover or are not reusable and some are not redeployable in the event it was found unnecessary to burn the oil. Furthermore, those which depend upon wicking to function often can plug because of contamination by silt or salt water. These problems lead to less than desirable performance and high cost.